Deep soil ectomycorrhizal communities of beech forests
Research Project | 5 Project Members
Ectomycorrhizal fungi (EMF) form symbioses with trees and provide key services related to nutrients
and water uptake that are essential for tree health. The symbiosis is increasingly in focus because of
concerns about forest health due to climate change, in particular tree resilience to drought. Deep
routing plants are typically more resistant to periods of drought and their root distribution patterns
across different soil depths is well understood. In contrast, little is known about EMF species and their
functioning in nutrient and water supply in deep soil layers. Furthermore, EMF functioning is often
compromised due to additional environmental stress, for example nitrogen deposition, soil
acidification or drought. EMF distributions and investigations on environmental effects in deep soil
layers are notoriously difficult to study and therefore, current knowledge is primarily limited to near-
surface horizons, mainly down to 10 cm or 25 cm soil depth. This project is specifically ‘digging deeper’
down to 100 cm and takes advantage of the long-term forest observation monitoring network
consisting of 21 beech forest sites in Switzerland. The network exists since 1984 and covers large
gradients in nitrogen deposition, soil chemistry and drought with a wealth of meta-data, including tree
vitality, for holistic interpretation. The key experimental resource, however, is the archive of 2100 EMF
samples from soil cores collected from layers down to 100 cm. Here, we make use of improvements in
DNA extraction from small amounts of EMF mycelium and highly accurate long-read sequencing to
characterise the EMF communities in deep soils. Half the samples from the archive consist of EMF
mycelium collected from so called ingrowth mesh bags and the other half are root tip samples collected
at the same depths. The ingrowth mesh bags function as ‘enrichment traps’ that enable sampling of
pure fungal mycelium and, therefore, provide a unique opportunity to specifically study deep soil fungi.
With this project we will characterize the deep soil EMF communities at high resolution and uncover
their abundance patterns in response to drought, N deposition and tree physiology. Furthermore, we
make use of the enrichment of EMF DNA within mesh bags to apply shotgun metagenomics. This will
permit novel and direct functional insights into deep soil EMF communities, advancing our
understanding of the role of EMF symbiosis in efficient exploitation of deeply located nutrient and
water resources for improved tree health.
